(1) Field of the Invention
The invention relates to a method of improving gate silicon oxide quality in the fabrication of integrated circuits, and more particularly, to a method of improving gate silicon oxide quality after ion implant in the fabrication of gate electrodes for an EPROM integrated circuit.
(2) Description of the Prior Art
Ion implantation to dope the substrate is a common practice in semiconductor manufacturing. For example, a threshold voltage ion implant is typically performed through a gate oxide layer into the semiconductor substrate before the formation of a gate electrode. A photoresist layer protects those areas of the substrate where the ion implantation is not desired. Both the ion implantation and the photoresist removal cause physical damage to the gate oxide layer causing degraded electrical breakdown and charge breakdown characteristics. This is especially critical with electrical programmable read only memory (EPROM) and erasable electrical programmable read only memory (EEPROM) devices.
U.S. Pat. No. 5,089,441 to Moslehi shows cleaning of metallic contaminants with halogen containing gas, such as HCl or HF. U.S. Pat. No. 5,225,355 to Sugino et al shows that HCl gettering can be used to clean or neutralize silicon oxide layers. No mention is made in either of these patents of damage to the gate silicon oxide caused by ion implantation.